Whisk 2 eggs and 100 grams sugar until the sugar dissolves.
Add the 100 milligrams vegetable oil, 50 grams cacao and 75 grams chocolate chips (if using) to the eggs and mix again.
When the mixture is well combined, gradually add the flour and the baking powder. Mix to obtain a sticky, slighty runny dough. Cover the dough and let it sit in the fridge for at least half an hour to 2 hours.
When time is up take out the cookie dough from the fridge and make small, walnut-size balls.
Pour two tablespoons of caster sugar in a bowl. After shaping all the dough, roll the cookie balls in the caster sugar to coat generously all around.
Then place the cookies in an oven tray with oven sheet. Make sure to leave some space between the cookies as they will rise. Sprinkle with additional caster sugar.
Bake in a pre-heated oven at 160° Celsius (300° F) for about 10-12 minutes. If the cookies stay in the oven too long, they will dry out. Be careful to keep an eye on them while in the oven.
When time is up take the cookies out of the oven. Let rest for a few minutes. Sprinkle with caster sugar before serving.